5. Stopping and Continuing

The principal purposes of using a debugger are so that you can stop your
program before it terminates; or so that, if your program runs into
trouble, you can investigate and find out why.

Inside No value for GDBN, your program may stop for any of several reasons,
such as a signal, a breakpoint, or reaching a new line after a
No value for GDBN command such as step. You may then examine and
change variables, set new breakpoints or remove old ones, and then
continue execution. Usually, the messages shown by No value for GDBN provide
ample explanation of the status of your program—but you can also
explicitly request this information at any time.

info program

Display information about the status of your program: whether it is
running or not, what process it is, and why it stopped.